Electromagnetic circuit maker and breaker



Oct. 4, 1949. E. T. BURTON 2,483,723

ELECTROMAGNETIC CIRCUIT MAKER AND BREAKER Filed April 3, 1945 INVENTOR E 7. BUR TON A A rro/ewe v Patented Oct. 4, 1949 UNITED STATES PATENT orncs Everett T. Burton, Millburn. N. J assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application April 3, 1945, Serial N0. 586,393

2 Claims. (01. 175-294) This invention relates to circuit makers and breakers and particularly to contact protection of glass sealed contact devices.

The object of the invention is to protect the contacts of a switching device from the ill eilects of breaking an abnormally high current. It is known that certain types of load give rise to initial transient currents which may reach relatively high values, such for instance, as the ordinary tungsten filament lamp. In such a case the cold resistance of the lamp is very low in comparison to the hot resistance thereof, so that when a lamp circuit is closed the initial current is many times the normal amount. Usually this has no adverse effect on the various circuit elements for the period which is required for the lamp to reach incandescence is very short. There are however situations in which it is desired to use glass sealed contact elements to close such a. circuit and in which the contact device is adequate to carry the normal current, but wherein the contacts are subject to serious injury or destruction, if for instance, they are opened during the initial rush of current into the cold lamps. Such an operation might come about through various circumstances, as for instance, the chattering of the contacts which control the magnetic means which are used to operate the said contacts.

In accordance with the present invention means are employed responsive to the high starting current to hold the closed contacts firmly together so that they cannot break the circuit during the period of the starting transient. This takes the form of an extra winding to influence the magnetic circuit of the contacts of such proportions that it will not interfere with the normal operation of the circuits but will respond to an abnormal condition.

A feature of the invention is a locking means for a pair of circuit closing contacts responsive to an abnormal rush of current therethrough According to this feature an operating winding for the contacts is included in series with the said contacts but is so proportioned and arranged that it will not prevent the opening of the contacts when a normal amount of current is flowing therethrough.

The drawings consist of a single sheet having two figures as follows:

Fig. 1 is a schematic circuit diagram illustrating the invention; and

In Fig. 2 the contact device consists of a glass envelope l into one end of which a tube 2 is sealed and which may be used during the construction for tubulation purposes and later when the device is in operation as an electrode. An element 3 of magnetic material is welded to the electrode 2 and a multiple armature 4 of magnetic material is welded to a spring 5 which is also attached to the electrode 2. At the other end of this device a magnetic element 6 is welded to a lead-in terminal 'l in such a position that gaps are provided between the elements 3, 4 and 6. A back contact element is also provided by the non-magnetic piece 8 welded to another lead-in terminal 9. This glass sealed element may be inserted within a coil and thus subjected to magnetic influence whereupon the element 4 is moved to decrease the gaps and make an electrical connection with the terminal piece 6 so that an electrical circuit may be completed through the device from the electrode 2 to the terminal 1.

Generally, these devices are evacuated and then filled with suitable gas such as hydrogen.

In the schematic circuit diagram such a device is illustrated by the element l0 carrying the two contacts I! and i2. This is shown in its unoperated position. In this circuit a lamp l3 represents a type of load which requires a high starting current such as an ordinary tungsten filament lamp which has a low cold resistance. The battery It may be closed to the load l3 through the use of any type of switch here illustrated by the switch l5. When the switch I5 is closed, a circuit will be extended from ground, battery I4 through the switch l5,,the main winding of the coil used for actuating the device It to ground. This will cause the contact elements I I and .l 2 to complete a circuit through the device so that now a circuit may be traced from ground, battery I4 through the auxiliary winding 16 of the contact device, the contact element H, the contact element [2, the load l3 to ground. The current flowing through this auxiliary winding will be heavy at first and will then decrease to the ordinary load current of the device I3. This starting current will be sufiicient to hold the contacts II and I2 closed even though in some manner the circuit for the main winding of the device becomes opened whereby the device is prevented from opening'a circuit with an extraordinarily heavy current flowing therethrough. After the operating current through the device l3 has subsided to its normal value, that current flowing through the auxiliary winding [6 will no means 3 longer be able to hold the contacts H and I! closed so that when the switch i5 is later opened the device will immediately release.

A resistance I1 is shown bridged across the auxiliary winding ii and this may be changed in value in accordance with the load which the device will be called upon to handle whereby the current through the auxiliary winding I6 may be properly adjusted. The resistance I1 is adjustable in the sense that different values may be provided to fit any particular circuit arrangement but it is not contemplated that this will be a variable type resistance.

A resistance It and a capacitor is in series therewith are bridged across the contact elements H and 12 to prevent arcing of the contacts on normal opening operations.

What is claimed is:

1. The combination of an electromagnetically operated circuit closer comprising a pair of contacts. an operating winding therefor and in series therewith, an external circuit closed for energizing andgde-energizing said operating winding to cause opening and closing of said first contacts at will, of an auxiliary winding for holding said contacts closed connected in series with said contacts responsive and effectively responsive only to current of a strength beyond a safe limit to be broken by said contacts.

2. An electromagnetically operated circuit closer having a predetermined mechanical bias providing a predetermined restoring force to hold said circuit closer in normally open position, an electrically operated solenoid in cooperative relationship with said circuit closer and external means including a source of current and a switch for energizing and de-energizing said solenoid at will to close and open said circuit closer at will, an auxiliary solenoid in cooperative relationship with said circuit closer. included in series with said source of current, said circuit closer and an external load, said auxiliary solenoid producing a magnetic effect to aid the holding ol' said circuit closer operated out of insufllcient strength to overcome said restoring force until the load current exceeds a predetermined value, whereby said circuit closer may be operated by said external means to break normal loads but will be prevented from responding to said external means to break greater than normal loads.

EVERETT T. BURTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 599,344 Murphy Feb. 22, 1898 733,551 Lindquist July 14, 1903 987,775 Van Volkenburg Mar. 28, 1911 1,336,158 Ream Apr. 6, 1920 1,443,583 MacGahan Jan. 30, 1923 1,500,800 Corichofi et a1. July 8, 1924 1,684,249 Stevenson Sept. 11, 1928 1,763,258 Ross June 10, 1930 2,320,208 Wurth May 25, 1943 2,358,198 Wyman Sept 12, 1944 2,397,123 Brown Mar. 26, 1946 

